1. Field of the Invention
The present invention relates to an intake quantity sensing device of an internal combustion engine.
2. Description of Related Art
For example, as described in the international publication pamphlet No. 03/033896, there is an air intake quantity sensing device that has intake pressure sensors in intake pipes of respective cylinders of an internal combustion engine for sensing air intake pressure and that calculates air intake quantities of the respective cylinders based on the intake pressure sensed with the intake pressure sensors of the respective cylinders. When intake pressure difference as a difference between a present value and a previous value of the intake pressure becomes equal to or greater than a predetermined value, the device determines that an acceleration state occurs and calculates an acceleration period fuel injection quantity in accordance with the intake pressure difference and engine rotation speed.
The above-described technology uses the intake pressure sensors provided for the respective cylinders of the engine. Therefore, it is necessary to provide the intake pressure sensors of the same number as the number of the cylinders, increasing the cost correspondingly. Specifically, in recent years, the number of the cylinders of the engine tends to increase, causing the problem of the increase in the range of the cost increase according to the increase in the number of the sensors.
A delay occurs between a time when a throttle opening degree changes during transient operation of the engine and a time when an output of the intake pressure sensor changes. The above-described technology calculates the intake quantities of the respective cylinders based on the intake pressure sensed with the intake pressure sensors without discriminating between a steady operation period and a transient operation period of the engine. Therefore, the intake quantity (in-cylinder filling air quantity), which changes in retard of the change of the throttle opening degree during the transient operation, cannot be calculated with sufficient accuracy. The technology merely calculates the fuel injection quantity at the time of the acceleration according to the intake pressure difference and the engine rotation speed at the time of the acceleration determination. Therefore, air-fuel ratio controllability during the transient operation cannot be improved sufficiently.